{"id":6534,"date":"2020-03-11T10:25:30","date_gmt":"2020-03-11T09:25:30","guid":{"rendered":"https:\/\/www.mio.osupytheas.fr\/fr\/comment-les-iles-du-pacifique-tropical-peuvent-elles-fertiliser-le-plancton-a-distance\/"},"modified":"2020-03-11T10:25:30","modified_gmt":"2020-03-11T09:25:30","slug":"how-the-islands-of-the-tropical-pacific-can-fertilise-plankton-from-a-distance","status":"publish","type":"post","link":"https:\/\/www.mio.osupytheas.fr\/en\/comment-les-iles-du-pacifique-tropical-peuvent-elles-fertiliser-le-plancton-a-distance\/","title":{"rendered":"How can islands in the tropical Pacific fertilise plankton from a distance?"},"content":{"rendered":"
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The fertilising effect of islands on the plankton in their surrounding ocean environments was discovered over sixty years ago. Now, researchers at the Institut m\u00e9diterran\u00e9en d'oc\u00e9anologie (MIO\/PYTH\u00c9AS, CNRS \/ Universit\u00e9 de Toulon \/ IRD \/ AMU) and the Laboratoire d'oc\u00e9anographie physique et spatiale (LOPS\/IUEM, UBU \/ Ifremer \/ CNRS \/ IRD) have demonstrated for the first time that islands can also fertilise distant ocean waters. This \"delayed island effect\" may be responsible for a very significant biological enrichment of the poor waters of the tropical Pacific, located far from any land.<\/p>

In the poor waters of the tropical Pacific, islands are sources of nutrients for microscopic photosynthetic algae, or phytoplankton, in the surrounding waters. The result is an enrichment of phytoplankton - a \"bloom\" - in the ecosystems near the islands. This fertilising effect, known as the \"island effect\", is reflected in an increase in chlorophyll concentration, which can be identified by satellite observations.<\/p>

In 2015, during the OUTPACE oceanographic campaign, a spectacular bloom was observed by satellite in the tropical south-west Pacific, a few hundred kilometres from the Tonga Islands. Scientists on the oceanographic vessel Atalante spent 5 days sampling this bloom. They found that it was made up of a nitrogen-fixing phytoplankton called Trichodesmium, which needs a lot of iron to grow. Such blooms, far from land, are generally attributed to local vertical processes of mixing or upwelling, which introduce nutrients from the depths into the surface layer where the phytoplankton can develop. Surprisingly, the physical measurements taken at this site showed that the iron could not have been brought in either vertically or by atmospheric deposition.
The scientists hypothesised that the waters must have been enriched with iron during their passage near the Tonga Islands a few weeks earlier. Unlike the organisms often associated with island effects, Trichodesmium develops very slowly. Its bloom can therefore occur several weeks after its fertilisation, possibly hundreds of kilometres from the islands following its transport by ocean currents.<\/p>

This hypothesis was tested by researchers at MIO and LOPS using a simple model representing phytoplankton growth in water masses fertilised by islands, while tracking their movement along trajectories calculated from ocean currents estimated by satellite.
The chlorophyll concentration maps obtained with the model are very similar to the satellite data acquired during OUTPACE, demonstrating that the islands were indeed able to trigger the bloom from a distance. These 'delayed island effects' may therefore be responsible for spectacular blooms with no apparent local origin, particularly in the warm waters of the tropical Pacific where Trichodesmium is common.<\/p>

Source<\/p>

Messi\u00e9, M., A. Petrenko, A.M. Doglioli, C. Aldebert, E. Martinez, G. Koenig, S. Bonnet and T. Moutin, 2020. The delayed island mass effect: How islands can remotely trigger blooms in the oligotrophic ocean. Geophysical Research Letters, 47(2), e2019GL085282, doi:10.1029\/2019GL085282<\/p>

Contact<\/p>

Monique Messi\u00e9
MBARI
+1 831 775 1836
monique@mbari.org<\/a>
Anne Petrenko
MIO\/PYTHEAS
04 86 09 06 06
anne.petrenko@mio.osupytheas.fr<\/a><\/p><\/div><\/div><\/div> <\/div> <\/div> <\/div> <\/div> <\/div><\/div>","protected":false},"excerpt":{"rendered":"

L\u2019effet fertilisant des \u00eeles sur le plancton de leurs milieux oc\u00e9aniques environnants a \u00e9t\u00e9 d\u00e9couvert il y a plus de soixante ans. Or, des chercheurs de l\u2019Institut m\u00e9diterran\u00e9en d\u2019oc\u00e9anologie (MIO\/PYTH\u00c9AS, […]<\/p>\n","protected":false},"author":1,"featured_media":4489,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-6534","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-actualites"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/posts\/6534","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/comments?post=6534"}],"version-history":[{"count":0,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/posts\/6534\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/media\/4489"}],"wp:attachment":[{"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/media?parent=6534"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/categories?post=6534"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/tags?post=6534"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}